Same thing happened to my string trimmer when I began using it last summer. The 87 octane 10% ethanol/gas mixture I had used in it for the last 3 or 4 summers had ruined the carburetor and the price of replacing the carb made it more practical to just buy a new trimmer. Now I pay $.90 per gallon more for ethanol-free gas, but it should save me money in the long run if it prolongs the life of my new (almost) Echo trimmer.
Carburetor rebuild kits for small engines run about $5 at the local saw shop.